Damp Remediation on old farmhouse

don_carlos

Hello all,
This is my first post to boards.ie though I have read numerous posts which have been very helpful. I have recently purchased a 100 year old farmhouse with 250mm thick stone walls in West Cork. The building has been unoccupied for several years and suffers from severe dampness issues. There is a dry ditch surrounding the back and side of the house. We do plan to do some work to the roof in the Spring as well as relining and potentially capping the chimney which should help address some of these issues. However we are on a tight budget and have to tackle each room at a time. The dampest and most problematic room is the one we intend to address first and I wanted to get some advice from the boards here in terms of solutions.
The room is 3.68 m x 2.68 m in size. It had timber wall panelling mounted on the walls when we moved in which we have since removed as they were clearly rotting and trapping in moisture. As they stand now the walls are coated in a sand/cement mortar which is covered in black hyphal mould on 3 of the 4 walls and there is clearly still water coming in from the ground. The floors are concrete slab which were previously carpeted. The dry ditch does run along the outside perimeter of these walls, though the back exterior wall is at the bottom of a steep slope so there is likely a lot of water runoff from here.
We have had a damp specialist in who has advised installing a vent through the wall to allow air circulation and to get rid of the intense humidity. His recommendation is to clean the mortar with a mould killer and then install a high density polyethylene membrane to the wall. He has quoted us €1500 for the installation of the waterproofing membrane and an additional €350 for the vent.
My questions are, does this seem like an adequate solution for the dampness issues, and a fair price for the work? We are eager to proceed with work so that the house is more liveable and we can move in our belongings without the fear of everything we own getting mouldy.
Thank you very much in advance for your help!

Sausage dog

We bought a very damp house, stone built & derelict for a few years.I'm no expert but based on what worked for us I'd say the first thing is to check the ground level outside compared to floor level inside. Lower the ground level outside & put in proper drainage around the house that draws water away from the house. We put in new concrete floors with damp proof membrane, insulation etc. and got a damp specialist to pump chemical dpc into walls to deter rising damp. Also check that downpipes aren't embedded in render & leaking thereby allowing water ingression to the walls.

don_carlos

Thanks for your reply, sausage dog. Has your house dried out pretty thoroughly? Happily the ground level outside is lower than the inside floor level and we do have a dry ditch around the house though the gutters need to be improved which we will address when we tackle the roof in the spring.If we decide to go this route we will likely use the polyethylene membrane over the concrete floor as well before laying engineered flooring so hopefully this will address these issues!

Calahonda52

OP, it seems you have a damp specialist who is also selling solutions which is NEVER a good idea.
Does the concert floor have a function DPM, you post is silent on this point.
What is the outside wall finish?
How exposed is the site?

Are the internal walls fully plastered with sand a cement render
so 350 for one hole in the wall?
Is that the extent of his ventilation ideas?

TBH, I would have little or no faith in this high density polyethylene membrane as it will have to be like an airtightness layer so how will it deal with internal walls, window reveals, floor joist in walls, roof wall-plate, electric sockets, etc etc.

I have,as have others, posted frequency on these issues so search this site for such posts
eg
http://www.boards.ie/vbulletin/showthread.php?t=2057692946

I have no great experience in this but a room by room approach doesn't sound like the best approach - a holistic approach would probably be better.

What other changes have you planned?
New windows, extension?

Have you considered mechanical ventilation?

Edit: I lived for a while in a small cottage that had been upgraded over the years - new windows, pumped insulation, central heating. The overall effect was to trap moisture in the house causing mould. Hole in the wall ventilation didn't work.

don_carlos

Hi Calahonda, thanks for the advice. I have tried to find as many relevant threads on the site here as I can and have found them very helpful. The concrete floor does not have a DPM, the idea was to run the polyethylene membrane on top of the floor and then refloor it with engineered wood flooring. The membrane would run the length of the walls and out a trench we'd dig out of the concrete around the perimeter of the room. It would wrap around the window boxes and behind the radiators/pipes, up the length of the wall. Apparently it comes in sheets which can be taped with an overhang between joints.
The walls are fully mortared on the inside. Two of the external walls (east and south) are exposed stone and the third north facing back wall is rendered with some kind of waterproof coating over it, though I am not experienced enough to identify the material. The 4th interior wall is the back of our chimney and has stayed dry and mould free.
The 350 includes the vent and 6" hole through the wall, we would self install. We would likely install another one in the adjacent room, in addition to using humidifiers while the house dries out.
The house is at the bottom of a hill and the surrounding grounds are covered in trees, apart from the south-facing front of the house which faces the road.

don_carlos

Hi pg633,
I agree that the holistic approach would be ideal but as we are on a tight budget we need to tackle the biggest issues first and wait a year or two until we can improve the rest of the house. We intend to improve the roof in the spring when it's drier. I do believe that much of the dampness in the house stems from the room we're trying to improve, and that between the roof and stopping moisture coming in from this room much of the rest of the house will dry out- the rest of the house is in much better condition than the northeast facing room.
Thanks for your reply!

Calahonda52

Don, thanks for the reply.
The correct terminology is important here so as we can point you to the right areas to explore.

I asked:
Are the internal walls fully plastered with sand a cement render?
You reply
The walls are fully mortared on the inside.

I don't understand what you mean by fully mortared.

Neither do I understand this
The membrane would run the length of the walls and out a trench we'd dig out of the concrete around the perimeter of the room

How big is this room? and how wide will this trench be?

I agree 100% with pg633 re a whole house approach but was waiting till we get a good understanding of the house: his other points are very telling..

Was you damp expert not able to identify the north wall finish?

My initial view is that you need to secure the roof if it is leaking and then look at MHVR for the whole interior so as to remove the damp air and replace it with fresh air. You may need to consider dehumidifying the air intake, given your location and the damp in the house.
Are you close to the sea?

smjm

I'm no expert, but unless the internal and external render/plaster is breathable, you're likely to have ongoing damp problems. Breathable would apply to any paint used as well as the material itself. Obviously the house didn't always have damp, so do you know the history of the house and what is or isn't original? Either way, you need to do a lot more research before you start doing any work which could just waste your budget and actually add to the problems. IMHO, keep away from damp specialists unless they can prove that they understand older buildings and can back it up with a portfolio of previous work on properties similar to your own -- which is doubtful!

Maybe have a look at some of the videos on this channel to provide food for thought: https://www.youtube.com/user/stibnite11/videos?sort=dd&flow=grid&view=0

Good luck!

Edit: uploading a few photos on a blog would be useful for the real experts. Starting a blog might also help you keep track of your project. Doesn't cost anything if you use wordpress or similar.

SmartinMartin

I've done a bit of digging into this recently. Bear in mind that the house was most likely originally rendered in lime mortar, making the walls breathable, thus allowing damp to escape. If it's been plastered in cement and concrete floors put in at some time in the past this will have trapped moisture and may be the cause of your problems.

don_carlos

Sorry, I meant that the internal walls are fully plastered with sand/cement. The room is 2.68 x 3.68 m2. The trench would be about an inch wide around the floor to allow the membrane to run out of the base of the floor (the membrane is about 10 mm thick). This is supposed to run the water away from the base of the house and into the dry ditch. We are about 25 km from the sea. The roof is not leaking into the house however after installing an access panel in the roof void I have seen that the plywood underlay that the felt/slates rest on is damp and some of the joists have moderate water damage. Some of this could be from the chimney which we are also planning to get work done to.
I certainly won't rule out MHVR in the future but at the moment I believe it is out of our budget, thanks for the tip!

Calahonda52

Okay Don ,some very useful stuff added by the others: Thanks guys and gals:)

The consensus here Don is that the 1,500 spend is the wrong answer right now so you need to step back a bit.
My view is that the 1,500 is a waste of money right now for the implicit and explicit reasons I and others have alluded to.

don_carlos wrote: »

Sorry, I meant that the internal walls are fully plastered with sand/cement. The room is 2.68 x 3.68 m2. The trench would be about an inch wide around the floor to allow the membrane to run out of the base of the floor (the membrane is about 10 mm thick). This is supposed to run the water away from the base of the house and into the dry ditch. We are about 25 km from the sea. The roof is not leaking into the house however after installing an access panel in the roof void I have seen that the plywood underlay that the felt/slates rest on is damp and some of the joists have moderate water damage. Some of this could be from the chimney which we are also planning to get work done to.
I certainly won't rule out MHVR in the future but at the moment I believe it is out of our budget, thanks for the tip!

I just can't get my head around this underlined concept
25 km from sea is good so the MHVR should work without out any special considerations.
Plywood underlay: are you sure?

MHVR may be out of your budget now but rushing now to spend 1,500 on what is a sub optimal solution is plain wrong.

I am signing off here now so good luck and keep well.

http://www.josephlittlearchitects.com/articles

don_carlos

Thanks Calahonda, I will take everything said here into consideration and wait and think on it before rushing into things. Certainly don't want to be wasting money on something that will not address the issue. Thanks for the help!

BryanF

Hi I stopped reading at 100 year old house and skipped to your latest post about money's tight - this is always the case, but it's an old house so modern methods don't always suit.

You have two options: You either pay someone else to this right or you do the hard work yourself!

Dig out the concrete floors.
Ensure external ground is 200+ mm below internal floor level on all sides, put in French drain.
Get independent advice on how to install a dpc in the rising walls
Hack of the cement wall render, replaster with lime, inside and out - consider floor and breathable wall insulation before replastering.

Best of luck

enricoh

Buy a mobile home for a couple of grand and a decent kango and wheelbarrow as the above poster said.
U'll have nothing but chest infections etc living in it doing up a room or two a year